Seoul’s YTN news channel ­reported on Wednesday that the 18-year-old student “had safely ­arrived in a third country”.

A source told the Post that the youth, identified as Jong Yol-ri, was accompanied by staff from the South Korean consulate and the Hong Kong government to the city’s airport where he boarded a flight for Seoul about a week ago.

“It was a night flight,” the source said.

Steve Chung Lok-wai, an ­expert in Korean affairs at Chinese University, said the reference to the “third country” could be interpreted as South Korea itself, in the context of North Korea as the first country, and Hong Kong in China as the second. South Korea would be the most straightforward destination, he said.

According to YTN, Jong – who defected while in town to attend a maths competition – intends to further his studies outside South Korea.

The Post was told the student was likely to settle in the United States after a couple of months.

The South Korean consulate, where Jong sought refuge after sneaking away from the 57th International Mathematical Olympiad on July 16, did not respond to the Post’s inquiries.

“We have no information to offer on this issue,”a Hong Kong government spokesman added.

At a regular press briefing in Beijing, Foreign Ministry spokesman Lu Kang said: “We have gathered preliminary information [about the defector’s situation], but there are many areas that ­remain unclear.”

The number of plainclothes police officers stationed at the Far East Finance Centre in Admiralty, which houses the South Korean consulate, appeared to have been reduced to just two on Wednesday.

A police source told the Post that enhanced security in place at the consulate since diplomats sought their help last month would continue.

Jong, a two-time silver medallist who had just picked up a third at this year’s maths contest, was staying at the Hong Kong University of Science and Technology, where the annual olympiad was held, before he left his five teammates and fled.

He is the first known North Korean to defect in Hong Kong since the city’s handover to China in 1997.

Security around the South Korean consulate was visibly stepped up after he sought refuge there. It was understood that uniformed and plainclothes officers from the counter-terrorism unit were deployed there.

Chinese University academic Chung said the defector’s departure was likely to have been ­endorsed by the Beijing ­government.

Owen Lau Kwun-hang, founder of the North Korean Defectors Concern group in Hong Kong, suggested Jong would remain in South Korea and seek citizenship there,